DIY 10dB Pi-Attenuator

Submitted by gerry on Thu, 02/09/2017 - 09:26

Attenuators are expensive, especially the fancy calibrated ones, and it seems that they are the only ones available. SMD resistors are cheap, though, and I have SMA connectors, so I thought I would try to make my own. I used the calculator here, to come up with a design that used resistors I had, gave an impedance of 50 ohms and an attenuation that was useful (10dB). The schematic for the attenuator is as follows. 

Parental Control using OpenWRT

Submitted by gerry on Tue, 02/07/2017 - 22:47

As a parent, I am somewhat torn regarding 'parental control' of Internet Access where my daughter is concerned. She is 8, so has limited access anyhow, but I would like for that access to be as unrestricted as possible while at the same time avoiding her stumbling any age-inappropriate content, which as we all know can often be only 2 or 3 clicks away.

I have decided on a multipronged approach, with the main home router, a TP Link N600 running OpenWRT Chaos Calmer being the crux of this.

Reflashing the Meraki MR12 AP with OpenWRT

Submitted by gerry on Mon, 01/30/2017 - 22:45

Meraki (now part of Cisco) are well known for their high-quality enterprise grade networking hardware. Over the last number of years, they have been promoting their kit by way of providing 'evaluation' units for the cost of simply attending a webinar. They specify that the attendee should be a 'networking professional', but it is possible that not every attendee is.
I recently acquired a number of these, where the evaluation period had expired, and the cloud-management interface was no longer accessible without a license key. This in effect makes the unit useless. Unless...

Morse Code Beacon for the Raspberry Pi

Submitted by gerry on Wed, 08/10/2016 - 22:38

Among other great features of the Raspberry Pi is the General Purpose Input Output array (GPIO). This is an array of pins that can be programmed to behave as pretty much any I/O type that can be represented digitally. The pins can be switched on or off to represent binary 1s and 0s and controlled so as to emulate any communication protocol that uses bits (I2C, SPI, RS232 etc. etc.). However, as a first attempt at working with GPIO, I took a recommendation from Steve EI5DD and wrote a program that will key a transceiver and generate morse code.

SSTV on Raspberry Pi

Submitted by gerry on Thu, 06/16/2016 - 16:19

Following a suggestion by Galway VHF Group mamber Steve, EI5DD, I thought I would give SSTV a shot. It's not a mode I have any experience with, apart from hearing the transmissions at 14.230MHz when I tune around. Steve mentioned a cross-platform SSTV program QSSTV, which seems to run well on a Pi 2, so that's what I decided to use.


a small matching unit to use the watson w2000 triband antenna on 70mhz

Submitted by gerry on Tue, 05/17/2016 - 15:34

I recently upgraded my shack to an ICOM IC7300, which in the EU specification includes the 4 meter / 70MHz band. I do not have a vertical for 4m, or space for one right now, but had read about others using a small matching unit to provide the necessary match using the Diamond V2000, or Watson W2000, as my version is badged.

Plotting Antenna Response using a Wobbulator and Return Loss Bridge

Submitted by gerry on Fri, 05/13/2016 - 15:21

At the Mayo Amateur Radio Rally a couple of years ago, a NI ham, Tom Herbison, MI0IOU was selling an interesting kit for the Raspberry Pi. It combined an Analogue Devices Clock Generator (AD9850) and an RF power meter (AD8307) to give a programmable sweep generator & detector... commonly known as a Wobbulator. I bought one and had anenjoyable afternoon not long afterward building it. It was a relatively easy build, and I got some use out of it tuning some Band Pass Filters I had built for use on multi-station portable ops.

HackRF One + CubicSDR on Ubuntu 15.10

Submitted by gerry on Wed, 03/30/2016 - 15:17

I have been playing with Software Defined Radio for a number of years, but recently advances in high-speed sampling has put relatively high quality, extremely high frequency SDR within reach of everyone. A few years ago Eric Fry reverse-engineered the communications from a Digital TV USB Dongle to see that it transmitted raw samples.